1. Field of the Invention
The present invention concerns the general field of infrared imaging and, more generally, the field of infrared imaging in ambient temperature.
2. Description of the Prior Art
Infrared imaging works on the following principle: infrared radiation absorbed through a layer of pyroelectric material causes a rise in temperature /T in the layer which itself gives rise to a quantity Q of surface electrical charges, such that: EQU Q=A.P.sub.Y..DELTA.T
where A represents the surface of the layer receiving the radiation and P.sub.Y is its pyroelectric coefficient.
As a rule, the relief of the electrical charges induced in a pyroelectric layer by an incident radiation is read by means of an electron beam in a vacuum tube (described in the article by M. BLAMOUTIER, P. CUNIBERTI, P. FELIX and S. VERNON, "Le Pyricon: un tube de prise de vue pour le domaine infrarouge thermique" (The Pyricon: A Pick-Up Tube For The Thermal Infrared Range) in the journal "L'Onde Electric", 1981, vol 61, No. 10, pp. 25 to 28) or by means of a plane matrix of switches associated with charge transfer lines (2D detectors such as those described in GB 2 200 246 and in the article by N. BUTLER, J. McCLELLAND and S. IWASA, "Ambient Temperature Solid-State Pyroelectric IR Imaging Arrays" in SPIE, vol. 930, Infrared Detectors and Arrays, 1988, pp. 151 to 163).
This technology of 2D detectors uses hybrid structures that are difficult to make and very costly. The difficulty of making these 2D detectors and their high cost are due to the complexity of these structures. For, instead of using a uniform pyroelectric tube as in the Pyricon tube, 2D detectors have as many pyroelectric elements as there are picture elements or pixels. These pyroelectric elements are moreover placed on electrically conductive but heat-insulating blocks that provide for the electrical connection between the pyroelectric elements and an underlying semiconductor substrate. The small dimensions of the pyroelectric elements (about 200 .mu..times.200 .mu.) and connecting blocks (having a section of about 50.mu..times.50.mu.) makes these structures all the more difficult to build as a large number of pixels is desired.